Firstly a frame structure in the existing Long Term Evolution (LTE) Time Division Duplex (TDD) system (in the LTE Rel-8/9/10/11/12/13) will be introduced below.
FIG. 1 is a schematic structural diagram of an LTE TDD frame, and as illustrated, the Frame Structure Type 2 (FS2) is applied to the existing LTE TDD system, and in the TDD system, there are different sub-frames or timeslots, at the same frequency, for uplink and downlink transmission. In the FS2, each 10 ms radio frame includes two 5 ms half-frames, and each half-frame includes five 1 ms sub-frames. The sub-frames in the FS2 are categorized into three categories: downlink sub-frames, uplink sub-frames, and special sub-frames, and each special sub-frame includes three components of a Downlink Pilot Time Slot (DwPTS), a Guard Period (GP), and an Uplink Pilot Time Slot (UpPTS). Table 1 depicts seven uplink-downlink sub-frame configurations supported in the FS2. Ten configurations for special sub-frame as depicted in Table 2 have been supported in the LTE Rel-13, and in each configuration, the lengths of symbols in a DwPTS and an UpPTS are specified, and the length of a GP can be determined as the difference between the total number of symbols in a sub-frame, and the lengths of symbols in the DwPTS and the UpPTS. In Table 2. X is a value configured in higher-layer signaling to additionally extend the length of the UpPTS, and X=2 or 4 symbols are supported, so that a part of the GP is allotted for the UpPTS. A downlink pilot, downlink service data (e.g., a downlink shared channel), and downlink control signaling (e.g., a downlink control channel) can be transmitted in the DwPTS, no signal is transmitted in the GP, and only a random access and a Sounding Reference Symbol (SRS), but neither uplink service (e.g., an uplink shared channel) nor uplink control information (e.g., an uplink control channel) can be transmitted in the UpPTS.
TABLE 1Uplink-downlink sub-frame configurationUplink-Downlink-downlinkto-Uplinkconfig-switch-pointSub-frame numberurationperiodicity012345678905msDSUUUDSUUU15msDSUUDDSUUD25msDSUDDDSUDD310msDSUUUDDDDD410msDSUUDDDDDD510msDSUDDDDDDD65msDSUUUDSUUD
TABLE 2Special sub-frame configurationNormal Cyclic Prefix (CP) in the downlinkExtended Cyclic Prefix (CP) in the downlinkUpPTSUpPTSSpecialNormalExtendedNormalExtendedsub-framecyclic prefixcyclic prefixcyclic prefixcyclic prefixconfigurationDwPTSin the uplinkin the uplinkDwPTSin uplinkin uplink0 6592 · Ts(1 + X) · 2192 · Ts(1 + X) · 2560 · Ts 7680 · Ts(1 + X) · 2192 · Ts(1 + X) · 2560 · Ts119760 · Ts20480 · Ts221952 · Ts23040 · Ts324144 · Ts25600 · Ts426336 · Ts 7680 · Ts(2 + X) · 2692 · Ts(2 + X) · 2560 · Ts5 6592 · Ts(2 + X) · 2192 · Ts(2 + X) · 2560 · Ts20480 · Ts619760 · Ts23040 · Ts721952 · Ts12800 · Ts824144 · Ts———913168 · Ts———
Feedback timing of Acknowledgment (ACK)/Negative Acknowledgement (NACK) for a Physical Uplink Shared Channel (PUSCH) in the existing LTE TDD system will be described below.
In the existing LTE TDD system, a Physical Uplink Shared Channel (PUSCH) is only transmitted in an uplink sub-frame. A UE transmitting a PUSCH in an uplink sub-frame numbered n receives a Physical Hybrid-ARQ Indicator Channel (PHICH) in a downlink sub-frame numbered n+kPHICH to obtain ACK/NACK feedback information of the PUSCH, where the HARQ stands for a Hybrid Automatic Repeat reQuest, and kPHICH is defined as depicted in Table 3; and if the PHICH carries NACK, then the UE will retransmit the PUSCH according to transmission configuration of an immediately preceding PUSCH. Moreover the UE further needs to detect the sub-frame, in which the PHICH is detected, for a downlink control channel with a Downlink Control Information (DCI) format in the uplink (a downlink control channel carrying an uplink (UL) grant), where the downlink control channel includes a New Data Indicator (NDI). For dynamic scheduling, whether the NDI is inverted indicates whether there are new data, and for example, an NDI in a corresponding downlink control channel when the PUSCH is initially transmitted is 0, so if a downlink control channel with an NDI) is received in the sub-frame in which the PHICH is detected after the PUSCH, then the NDI will have not been inverted, so the PUSCH is scheduled by the downlink control channel to be retransmitted; and for semi-persistent scheduling, if the NDI is 1, then it will represent retransmission, and if the NDI is 0, then it will represent activation/deactivation scheduling signaling; and if the NDI indicates new data, then the first transmission of a new PUSCH will be scheduled by the downlink control channel, and if the NDI indicates retransmission, then retransmission of a preceding PUSCH will be scheduled by the downlink control channel. Accordingly both the PHICH, and the downlink control channel with the uplink DCI format can schedule retransmission of a PUSCH, and the downlink control channel with the uplink DCI format can also schedule transmission of a new PUSCH, i.e., initial transmission thereof. If both a PHICH and a downlink control channel are detected in a sub-frame for detecting the PHICH, then reference will be made to information in the downlink control channel, that is, whether to retransmit a PUSCH will be decided according to an NDI in the downlink control channel, and if so, then the PUSCH will be retransmitted according to scheduling information indicated by the downlink control channel (which may be different from scheduling information for initial transmission); and only a PHICH is received, and the PHICH indicates NACK, then the PUSCH will be retransmitted according to the same configuration as initial transmission thereof. Accordingly the downlink control channel with the uplink DCI format may not be detected in the sub-frame for detecting the PHICH, and if no downlink control channel is detected, then whether to retransmit the PUSCH will be decided according to the feedback information carried in the PHICH; and if the downlink control channel is detected, then whether to retransmit the PUSCH will be decided according to the downlink control channel with the uplink DCI format.
Furthermore there is also defined a sub-frame in which the corresponding PUSCH is retransmitted or initially transmitted when the UE detects the downlink control channel with the uplink DCI format, and/or the PHICH, i.e., scheduling timing of the PUSCH, as depicted in Table 4. The UE adjusts the transmission of PUSCH in the sub-frame n+k according to the downlink control channel with the uplink DCI format, and/or the PHICH, detected in the sub-frame n.
TABLE 3kPHICH for TDDTDD UL/DLSub-frame index nconfiguration0123456789047647614646266366646656646647
TABLE 4k for TDD configurations 0-6TDD UL/DLsubframe number nConfiguration01234567890464616464244344444454677775
It shall be noted that the sub-frames are indexed in Tables 3 and 4 in the unit of a radio frame, and for a sub-frame indexed n+k, if n+k is greater than 9, then the sub-frame will be a sub-frame in a next radio frame.
A drawback in the prior art lies in that: in the existing LTE system, transmission of a PUSCH in an UpPTS in a special sub-frame is not supported, so scheduling timing of the PUSCH in the UpPTS in the special sub-frame has not been defined yet.